Igniter for a rocket engine, method for ignition of a rocket engine

ABSTRACT

An igniter for a rocket engine or motor comprising a combustion chamber with a solid fuel, an inlet for supplying an oxidizer to the combustion chamber to ignite the solid fuel and an outlet for discharging exhaust gas, wherein the igniter is arranged to discharge exhaust gas to the rocket engine for igniting the rocket engine. The igniter can be used for multiple ignitions and can also be re-used after re-filling.

The invention relates to an igniter for a rocket engine.

Igniters for a rocket engine are commonly known and widely used inaerospace applications such as aerospace rockets used for space launcherpropulsion. Known igniters may comprise a solid propellant. The solidpropellant is usually a mixture of solid fuel with a solid oxidizer. Themixture is prepared in a controlled and/or conditioned environment in afactory. Igniters using solid propellants are relatively simple indesign. A drawback of such igniters is that the transport of thepremixed propellant, e.g. from the factory location to the use location,and storage of the solid propellant is relatively difficult, dangerousand/or expensive in view of the ignition danger of the premixedpropellant. Another drawback of such igniters is that they can only beused once.

Also known are igniters that use spark ignition to ignite liquid and/orgaseous propellants. Igniters using spark ignition may be re-usable. Adrawback of using spark ignition is that relatively complex andexpensive electronics are required for controlling the sparks. Also, iftwo gases are used, this may require a relatively complex arrangementfor storing them separately.

Publication U.S. Pat. No. 3,518,828 discloses an igniter for a hybridrocket engine of which the solid propellant is ignited by a conventionalelectrical squib igniter.

Publication U.S. Pat. No. 6,250,072 discloses reignition of asolid-propellant gas generator using a reactive oxidizer such as hotnitrous oxide to inject into the gas generator chamber.

Publication U.S. Pat. No. 3,101,589 describes a method for ignitingrocket engines with hydrazine type fuels using solid oxidizers.

It is an object of the invention to provide an igniter for a rocketengine that obviates at least one of the above mentioned drawbacks whilemaintaining the advantages.

Thereto, the invention provides for a hybrid igniter for a rocketengine, the hybrid igniter comprising a combustion chamber provided witha solid material, an inlet for supplying a fluid product to thecombustion chamber and an outlet for discharging an exhaust gas, suchthat the exothermic reaction of the fluid product with the solidmaterial in the combustion chamber generates a combustion producing theexhaust gas, wherein the igniter is arranged to discharge the exhaustgas to the rocket engine for igniting the rocket engine.

By providing an igniter with a combustion chamber with a solid materialto which a fluid product is supplied, a hybrid igniter is obtained. Thehybrid igniter is relatively simple in design and construction contraryto a spark ignition system.

The solid material and the fluid product react with each other in thecombustion chamber. Such a reaction is known as an exothermic chemicalreaction and may result in an ignition and therefore in a combustion inthe combustion chamber. The solid material can be a solid fuel or asolid oxidizer, while the fluid product can be a fluid oxidizer or afluid fuel respectively. The combination and/or cooperation of theoxidizer with the fuel may result in an ignition and a combustion. Thefluid product may be liquid or gaseous. In an embodiment, the combustionchamber may be filled with solid fuel and the fluid oxidizer may besupplied to the combustion chamber via the inlet. In another embodiment,the combustion chamber may be filled with solid oxidizer and the fluidfuel may be supplied to the combustion chamber via the inlet.

Since the fuel is not mixed with the oxidizer in advance, the fuel canbe relatively easily and safely stored, transported and handled,separate from the oxidizer. There is no risk of e.g. spontaneousignition during storage and/or transport of the fuel. Also the oxidizercan be relatively easily and safely stored, transported and handled,separate from the fuel.

The hybrid igniter can be used on different types of rocket engines forspace launcher propulsion, for example solid rocket motors, liquidrocket engines. The oxidizer can for example be liquid oxygen or liquidhydrogen peroxide. The fuel can for example be a solid or liquid polymeror hydrocarbon or any other suitable product.

By providing an initiating device the combustion in the combustionchamber may be started. The initiating device can be understood tocomprise any means that initiates a combustion process. The initiatingdevice may for example be a catalyst that decomposes the oxidizer. Thedecomposed oxidizer may facilitate the combustion of the solid fuel inthe igniter. The initiating device may also be a heating element thatadds heat to e.g. a fluid oxidizer supplied via the inlet to provideignition of the solid fuel in the combustion chamber. Alternatively, thefluid oxidizer may already be heated and/or catalyzed in advance beforebeing supplied to the igniter. In an embodiment, the initiating deviceis part of the igniter and is arranged between the inlet and thecombustion chamber. The igniter thus can be of relatively compact designwhile the efficiency of the combustion can be increased. Alternatively,the initiating device may be provided in the combustion chamber itself,e.g. when the combustion chamber is provided with solid oxidizer. Theinitiating device can then e.g. be a heating element for heating theoxidizer. Also, as an initiating device, the solid material in thecombustion chamber may e.g. be provided with a top layer of a reactiveproduct and/or of a specific constitution such that it ignites as soonas the fluid product contacts the top layer. The top layer may e.g.comprise catalyst powder. Also, as an initiating device, in the inlet afew droplets of aggressive fluidum may be sprayed or otherwise providedbefore the fluid product flows through the inlet. In the combustionchamber the aggressive fluidum provides for an ignition when reactinghypergolically with either the solid material or fluid product.

By providing an injection element, the fluid product can be injected tothe combustion chamber, thereby increasing the efficiency of theignition and/or combustion of the solid material. Preferably, theinjection element is arranged at or in the inlet, for example downstreamthe inlet and upstream the initiating device. In an embodiment, theinjection element can also be provided in the inlet or as part of theinlet.

Unlike a solid igniter the hybrid igniter can be re-used, re-ignitedand/or throttled. By providing a control element, the igniter can bere-used, re-ignited and/or throttled in a controlled and/or predictableway. The control element is arranged for controlling the supply of thefluid product. The control element can e.g. be a valve that controls thesupply of the fluid product. The control element may be installed at orin the inlet or upstream in the supply line of the fluid product. Whenvarying the supply of the fluid product, the combustion can bethrottled. For re-use only the solid material needs to be replaced andre-ignition can be achieved by re-supply of the oxidizer. When the solidmaterial needs to be replaced, the valve can be closed, when re-ignitionis required, the valve may be opened to supply fluid product to thecombustion chamber to induce ignition and combustion. Throttling of thehybrid igniter can be performed by variation of e.g. the oxidizer flow.

The control element may usually be operated remotely, in view of thecomplex installation of a rocket engine. However, the control elementmay also be arranged to be operated manually.

After use the solid material is usually approximately completelyconsumed. The combustion chamber then may be cleaned, e.g. by ultrasoniccleaning, and a new block of solid material may be provided in thecombustion chamber. Thereto, the igniter is arranged for refilling thesolid material. The igniter may be provided with a part of a housing ofthe igniter that is removably connected to provide for an opening forrefilling the solid material. For example, the bottom or a segment ofthe walls of the combustion chamber can be removably connected, e.g. viaa bolt-nut connection or a screw connection. At the connection heatresistant seals may be used. Alternatively, the inlet and/or theinjector can be removably connected to the combustion chamber to providefor an opening for refilling the solid material.

Further advantageous embodiments are represented in the subclaims.

Further, the invention relates to a method for igniting a rocket enginefor space launcher propulsion.

The invention will further be elucidated on the basis of an exemplaryembodiment which is represented in a drawing. The exemplary embodimentis given by way of non-limitative illustration of the invention.

In the drawing:

FIG. 1 shows a schematic representation of an igniter according to theinvention.

It is noted that the FIGURE is only a schematic representation of anembodiment of the invention that is given by way of a non-limitingexample.

FIG. 1 shows an igniter 7 comprising a combustion chamber 4 which is atleast partially filled with a solid material. In this example the solidmaterial is a solid fuel 5. The solid fuel 5 can be based on e.g. HTPB(hydroxy-terminated polybutadiene), PMMA (polymethylmethacrylate), otherhydrocarbons or plastics. Fluid fuel may for example comprisehydrocarbons like ethanol, methane. Fluid oxidizer may for examplecomprise oxygen, hydrogen peroxide, a solid oxidizer may for examplecomprise ammonium perchlorate, ammonium nitrate. Further, the igniter 7comprises an inlet 1 for supplying a fluid product, in this exampleliquid or gaseous oxidizer to the combustion chamber 4. The oxidizerignites the solid fuel 5 which leads to a combustion of the solid fuel5. The inlet 1 may be coupled to a storage compartment of oxidizer.

The igniter 7 is a hybrid igniter by supplying a fluid product to asolid material. As a fluid product liquid oxidizer may be supplied,however gaseous oxidizer may also be used to ignite the solid fuel inthe combustion chamber. Alternatively, liquid or gaseous fuel may beused for combustion with a solid oxidizer in the combustion chamber. Theigniter 7 is applied in rocket engines for space launcher propulsion.Combustion of the solid fuel 5 produces hot exhaust gas that isdischarged from the igniter 7 via an outlet 6. The hot exhaust gas isdischarged to a rocket engine to ignite the rocket engine and to inducecombustion of the rocket engine. The outlet 6 of the igniter 7 usually,when installed, discharges the hot exhaust gas of the igniter 7 directlyinto an ignition chamber and/or combustion chamber of the rocket enginefor space launcher propulsion.

The solid fuel 5 in the combustion chamber 4 is used during combustion,so the volume of the solid fuel 5 becomes less during the combustion ofthe solid fuel 5. The free volume of the combustion chamber 4 thereforeincreases during combustion of the solid fuel 5. The combustion time ofthe igniter 7 is usually approximately 0.2-2.0 s, the rocket engine willbe ignited and combustion in the rocket engine may have been started.Further, the igniter 7 typically is relatively small in comparison witha rocket engine for space launcher propulsion, typically approximately100 to approximately 500 mm, more typically approximately 200 toapproximately 400 mm.

The combustion can be stopped or re-started at any time by providing acontrol element 8. In this example, the control element 8 is provided asa valve 8. The valve 8 is here connected to the inlet 1 and is arrangedfor starting, stopping and/or dosing the flow of the oxidizer. Byswitching off or on the flow of oxidizer, the combustion can be stoppedor started. By varying the flow of the oxidizer, the combustion can bethrottled. Of course, the control element also can be provided at adifferent position, e.g. upstream of the inlet in or at the supply linefor the fluid product, which may be oxidizer or fuel.

Further, the igniter 7 comprises here an initiating device 3 which canbe for example a catalyst or a heater. A catalyst may decompose theoxidizer, which is for example hydrogen peroxide, to induce ignition ofthe solid fuel 5 in the igniter 7. A heater can heat the oxidizer, forexample oxygen, until the ignition temperature of the solid fuel isreached. Alternatively, the oxidizer can be heated before being suppliedto the combustion chamber, e.g. in the inlet or between the inlet andthe storage compartment of oxidizer.

Further, the igniter 7 comprises in this embodiment an injection element2 to inject the oxidizer with relatively high pressure into thecombustion chamber 4. Injecting the oxidizer under high pressure intothe combustion chamber 4 may be advantageous for the ignition of thesolid fuel 5.

The injection element 2 is preferably positioned at or in the inlet 1.In this embodiment, the injection element 2 is placed immediatelydownstream the inlet 1, but upstream the initiating device 3. Theinitiating device 3 is placed upstream of the combustion chamber 4.

The hybrid igniter 7 as shown in FIG. 1 has a relatively simple designand can be re-used. For example, after use the solid fuel 5 is usedduring combustion and only a solid fuel element has to be placed in thecombustion chamber. A part of the housing of the combustion chamber maythereto be removably arranged, e.g. via a screw or bolt and nut or aclamp connection. For example a bottom part or an inlet part or a wallpart of the combustion chamber may be removable. Or the combustionchamber itself may be a compartment of the igniter which can be easilyreplaced after use of the igniter for re-use. Or the solid fuel may beprovided as a block or a cartridge that can easily be taken out of theigniter after use and a new block or a new cartridge can easily beplaced in the igniter for a re-use of the igniter.

Many variants will be apparent to the person skilled in the art. Allvariants are understood to be comprised within the scope of theinvention as defined in the following claims.

1. A hybrid igniter for a rocket engine, the hybrid igniter comprising acombustion chamber provided with a solid material, an inlet forsupplying a fluid product to the combustion chamber and an outlet fordischarging an exhaust gas, such that an exothermic reaction of thefluid product with the solid material in the combustion chambergenerates a combustion producing the exhaust gas, wherein the igniter isarranged to discharge the exhaust gas to the rocket engine for ignitingthe rocket engine.
 2. An igniter according to claim 1, wherein the solidmaterial is a solid fuel or a solid oxidizer, and the fluid product is afluid oxidizer or a fluid fuel respectively.
 3. The igniter according toclaim 1, further comprising an initiating device for inducing ignition.4. The igniter according to claim 3, wherein the initiating device isarranged between the inlet and the combustion chamber.
 5. The igniteraccording to claim 3, wherein the initiating device is arranged in thecombustion chamber.
 6. The igniter according to claim 1, furthercomprising an injection element for injecting the fluid product.
 7. Theigniter according to claim 6, wherein the injection element is arrangedat or in the inlet.
 8. The igniter according to claim 1, wherein acontrol element is arranged for controlling the supply of the fluidproduct.
 9. The igniter according to claim 8, wherein the controlelement is arranged for restarting the igniter.
 10. The igniteraccording to claim 1, wherein the igniter is arranged for refilling thecombustion chamber with solid material.
 11. A method for igniting arocket engine, comprising providing an igniter according to claim 1,supplying a fluid product to the igniter such that combustion of thesolid material is provided, supplying the exhaust gas to the rocketengine.